1. Field of the Invention
This invention relates to a printing timing correction device in a shuttle type dot line printer, and more particularly to an improved printing timing correction device in the shuttle type dot printer wherein a shuttle including a plurality of printing needles is oscillated in directions perpendicularly intersecting a direction of feeding printing paper.
2. Description of the Prior Art
There have heretofore been known dot printers, in each of which printing needles are projected to printing paper in accordance with predetermined printing data and desirable characters, signs and others are formed by a plurality of dots, being used as various output printing devices for information processing machines. Furthermore, there have been known as dot line printers, in each of which the above-described dot printer is further improved such that a plurality of printing needles are arranged at equal intervals in a line on the printing paper, while the printing needles are reciprocated across a needle pitch the paper feed is effected in a direction perpendicular to the directions of the reciprocation, to thereby conduct desired printing operations successively. The dot line printer is advantageous in that it can carry out the printing operations at very high speed and in large quantities as compared with a serial type dot printer. Since an oscillating portion reciprocating across a needle pitch, in which a plurality of printing needles are arranged, is referred to as a shuttle, the above-described printer is known as a shuttle type dot line printer.
FIG. 1 shows the conventional example of the shuttle type dot line printer of the type described, in which a platen 26 is rotatably supported by side walls 22 and 24 affixed to a base frame 20, and recording paper is placed along the surface of the platen 26. The recording paper is click-feedingly supported at opposite end edges thereof by paper feed receivers 30 and 32 and paper feed-driven by the rotation of a feed shaft 34 in the direction indicated by an arrow mark A.
The base frame 20 is provided thereon with a shuttle 36 reciprocatorily supported in directions B-C perpendicularly intersecting the aforesaid direction A for paper feeding. On the shuttle 36, there are regularly arranged a plurality of printing needles projecting to the recording paper 28, and these printing needles corresponding to predetermined positions are adapted to project to the recording paper in operational association with the reciprocatory motions of the shuttle 36, whereby simultaneous printing in a direction of a line are conducted on the recording paper 28 through a ribbon or the like. Although the construction of the respective printing needles 10 and a solenoid driving device are not shown in detail in the drawing, the arrangement similar to that of the normal dot printer is provided for each of the printing needles.
To reciprocate the shuttle 36 in the directions B-C, a driving motor 38 consisting of a DC motor or the like is affixed to the base frame 20, and a flywheel 40 is solidly secured to a shaft of the motor. A crankshaft, not shown, is provided in front of the flywheel 40. One end of a connecting rod 42 is engaged with the crankshaft and the other end thereof is engaged with the shuttle 36 through a shaft 44, so that it is readily understood that the shuttle 36 can be reciprocated in the directions B-C through a crank mechanism including the connecting rod 42 in accordance with the rotation of the driving motor 38.
The shuttle 36 includes therein a plurality of printing needles and printing needle actuators for driving the printing needles, and these driving portions are integrated into a hammer bank. The hammer bank is comparatively large in weight and its inertial force is high during the operation of the driving motor, whereby the hammer bank tends to cause unnecessary vibrations and the like to the device itself. To absorb the inertial force, the device is provided with a counterweight 46 reciprocating in a direction opposite to that of the shuttle 36. The counterweight 46 is connected to the aforesaid crankshaft through a second connecting rod 48, whereby the shuttle 36 and the counterweight 46 move in directions opposite to each other, and the inertial force and the reaction force caused by an acceleration offset each other through the utilization of the reaction forces of the both members, so that the vibrations are prevented from being caused to the device itself. The shuttle 36 and the counterweight 46 are respectively supported in their movements in the directions B-C by receiving bases 50 and 52 affixed to the base frame 20.
A slit disc 54 affixed to the tail end of the motor 38 electrically, accurately detects a position in the reciprocatory motion of the shuttle 36 in cooperation with a photointerruptor 56.
As apparent from the aforesaid FIG. 1, the shuttle 36 is reciprocated in the directions B-C by the crank mechanism, with the result that the reciprocatory motion of the shuttle 36 becomes a non-constant velocity motion as against the motor 38 performing a constant velocity motion. As it stands, it becomes difficult to accurately set the printing timing of the printing needles. Therefore, with the conventional device, there has been a problem that a compensating mechanism should be provided which mechanically correct the above-described non-constant velocity motion, so that the shuttle 36 can reciprocate at a constant speed. Because of this, the device is rendered large-sized and increased in manufacturing cost. Furthermore, in FIG. 1, a special cam configulation is required for the engagement between the connecting rods 42, 48 and the shaft of the motor 38. In that case, there has been presented the disadvantage that the working and the positioning at the time of assembling are quite troublesome.